Synthesis
(b) Synthesis of 2-chloro-6-(trifluoromethoxy)pyridine (1-5): a mixture of SbF3 (29.87 g, 167.10 mmol, 2 eq.) and SbCl5 (1.61 mL, 12.53 mmol, 0.15 eq.) was stirred at 120 °C under argon protection. Subsequently, 2-chloro-6-(trichloromethoxy)pyridine (20.63 g, 83.55 mmol, 1 eq.) was added slowly and dropwise over 20 min. The reaction mixture was continued to be stirred at 120 °C for 3 hours. Upon completion of the reaction, the mixture was cooled to room temperature and diluted with the addition of dichloromethane (350 mL), followed by the addition of saturated sodium carbonate solution (350 mL) and 20% KF aqueous solution (175 mL) sequentially. The resulting biphasic mixture was filtered through Celite. The organic and aqueous layers were separated and the aqueous layer was extracted repeatedly with dichloromethane (5 x 100 mL). All organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated to dryness. The crude product was purified by vacuum distillation (pressure = 35 mbar, temperature = 81-83 °C) to afford 2-chloro-6-(trifluoromethoxy)pyridine as a colorless oil in 62% yield.1H NMR (CDCl3) δ (ppm): 6.96 (d, 1H), 7.27 (d, 1H), 7.75 (t, 1H).
References
[1] Patent: WO2012/93174, 2012, A1. Location in patent: Page/Page column 38
[2] Patent: WO2010/40461, 2010, A1. Location in patent: Page/Page column 17-18
[3] European Journal of Organic Chemistry, 2010, # 31, p. 6043 - 6066
[4] ChemMedChem, 2015, vol. 10, # 4, p. 715 - 726
[5] Journal of Fluorine Chemistry, 2017, vol. 203, p. 155 - 165
